Patent GB-1219294-A (GB)
Title: Controller for diaphragm motor valve
IPC: G05D16/16
Filed: 1968-10-30
Abstract: 1,219,294. Fluid-pressure servomotor systems. AMERICAN METER CO. Oct.30, 1968 [March 4, 1968], No.51475/68. Heading G3P. A controller for pneumatically operating a diaphragm motor valve 10 in a pipeline 11, and continually moduating the valve 10 in respect to its delivered pressure comprises four axially spaced diaphragms 25, 30, 31 and 36 connected by a hollow spool 39, diaphragms 30, 31, 36 being of the same size, while the diaphragm 25 is larger, a chamber 130 between the diaphragms 25 and 36 communicating with a line 14 leading to the valve 10, a chamber 135 between the diaphragms 30, and 31 communicating with a pressure supply source 16, 18 taken from the line 11 upstream of the valve 10, a chamber 134 below the diaphragm 31 communicating with the line 11 downstream of the valve 10, the hollow spool connecting the supply chamber 135 with the output chamber 130, a rod 60 extending through the spool having a poppet 63 at one end to close the passage through the spool, and a poppet 62 at the other end for closing an exhaust port 138 from the output chamber 130, so that movement of the spool towards the chamber 130 opens the spool passage to connect the chamber 135 to the chamber 130, and movement in the opposite direction connects the chamber 130 to exhaust. A reference spring 96 which can be adjusted by rotation of a barrel 103 with a pressure gauge 107, opposes the line pressure acting in chamber 134 which causes the spool to move and an adjustable linkage 84 connects the spool and the diaphragm 25 to effect an output feedback and control the gain between the pressure change in the chamber 134 and the output pressure change at 130. The linkage 84 is formed by hooked members 76 mounted on the diaphragm 25, and connecting with arcuate members 83 pivoted in a collar 79 at one end, and locating in a groove 90 in the spool at the other end. Rotation of the collar 79, by a lever (81), Fig.3, (not shown), varies the position at which the hooks 76 engage the members 83, and consequently the moving force applied to the spool by the diaphragm. In operation, a reduction in flow requirements through the pipeline 11 results in an increase in pressure in the chamber 134, to move the spool 39 against the spring 96 and open the poppet valve 63, to allow pressure in chamber 135 to pass to line outlet 130 and act to close the valve 10, and to pass through a clearance around the spool 39 and act in a chamber 124 above the diaphragms 25. The downward force of the diaphragm is transmitted to the spool 39 via the linkage 84 to close the valve 63. A chamber 127 below diaphragm 31 is connected with the chamber 124 via an adjustable throttle 114, and the pressure in the chamber 127 acts on the diaphragm 25 to modify the downward movement of the spool 39, resulting in a gradual closing of the valve 10 and reestablishment of the pressure in chamber 134 to its previous value, and eventually the point set by spring 96. A drop in pressure in the chamber 134, resulting from an increase in flow requirements, allows the spool to move downwards to open valve 62 and exhaust the supply chamber 130 to outlet 138, to open valve 10. The pressure in the chamber 138 being gradually re-established by the mechanism 25, 84 and 118. The loading pressure of the spring 96 can be augmented by fluidpressure through connection 139. The spring 96 can be varied by a screw (142), Fig. 11, (not shown). The adjustable throttle can be replaced by a vent. The ports 18 and 134 can be combined. The valve 10 can be normally closed, in which case the valve construction is reversed with an end cap 28 connected to the upper part of body portion 20, and the loading spring engaging a washer 50.